1. Filed of the Invention
The present invention relates to a magnetic head apparatus using a metal evaporated type magnetic tape and a drive apparatus including a magnetic head apparatus.
2. Description of the Related Art
In recent years, in accordance with an explosive increase of a data amount, the increase of a storage capacity becomes the most urgent need in a tape-system storage system, and hence it is requested to increase a recording density to realize the above-mentioned increase of the storage capacity.
Under such circumstances, there is a trend that a so-called linear type magnetic recording tape system in which a magnetic tape is transported in the outward and inward direction and vice versa relative to a magnetic tape so as to record thereon data in a serpentine fashion is widely used increasingly.
However, in a magnetic tape formed of a coating type magnetic layer and which is now commercially available on the market, the increase of the recording density seems to reach its limit, and under the present circumstances, it cannot be expected that recording density will not be increased more than the present high recording density. For this reason, also in the linear type magnetic recording tape system, it has been discussed to use a so-called metal evaporated type magnetic tape for use in high recording density and if which magnetic layer is formed of a ferromagnetic metal evaporated film.
However, in the metal evaporated magnetic tape, its recording and reproducing characteristics become different depending upon the sliding direction in which a magnetic tape is slidably transported on a magnetic tape. The reason for this is that, since the magnetic layer is formed by rhombic vapor deposition of ferromagnetic metal, the magnetic layer has a rhombic pyramid structure to exhibit rhombic magnetic anisotropy.
So far there have been proposed metal evaporated type magnetic tapes in which difference between recording and reproducing characteristics in accordance with the sliding direction, that is, polarity can be improved (for example, see cited patent references 1, 2 and 3).
In these previously proposed metal evaporated type magnetic tapes, difference between recording and reproducing characteristics relative to the sliding direction can be improved by selecting factors of the magnetic layer, such as structure, film thickness and magnetic properties.
[Cited patent reference 1]: Official gazette of Japanese laid-open patent application No. 4-353621
[Cited patent reference 2]: Official gazette of Japanese laid-open patent application No. 4-353622
[Cited patent reference 3]: Official gazette of Japanese laid-open patent application No. 5-182168
In the linear type magnetic recording tape system, in order to increase the recording capacity more and to realize the higher recording density, it is requested to narrow the width of the recording track more. Concurrently therewith, it is requested to narrow the track width of the operation magnetic gap of the magnetic head. From these requests, as a recording magnetic head, there is used a thin film recording head having a microminiaturized structure that can be manufactured by a thin film technology in the semiconductor manufacturing technology.
In this thin film magnetic head, at least one of upper and lower magnetic cores comprising the operation magnetic gaps at their front portions is composed of a thin film magnetic layer, and the front portion comprising the operation magnetic gap of only one of the magnetic cores composed of the thin film magnetic layers is selected so as to have a narrow width having a target track width. In this manner, the magnetic core having the narrow front portion and the magnetic core having the wide front portion are opposed to each other to construct the operation magnetic gap, and the track width of the operation magnetic gap is determined by the narrow front portion. In the thin film magnetic head of this kind, while its operation magnetic gap has an asymmetric structure relative to the center surface, the track width is determined by the thin film magnetic layer processed with high accuracy and hence the track width of the operation magnetic gap can be microminiaturized with high accuracy.
Since the thin film recording head is manufactured with application of the thin film pattern technology used in the semiconductor manufacturing process as described above, a recording track width is accurate and it has less dispersions. Therefore, as compared with a conventional MIG (Metal in Gap) type magnetic head, this thin film magnetic head has an advantage such that it is suitable for the application to high-density tape systems such as a narrow track multi-channel linear system.
However, when data is recorded on the magnetic tape by the thin film head with the operation magnetic gap having the asymmetric structure as described above, complex magnetic fields are generated in the edge portion of the track width direction. Also, as mentioned hereinbefore, since the metal evaporated type magnetic tape has the rhombic anisotropy, when data is recorded on this magnetic tape, recording and reproducing characteristics of the thin film magnetic head and the metal evaporated type magnetic tape are inevitably changed so much during the magnetic tape is being transported in the outward and inward direction and vice versa.
Further, when data is recorded on the metal evaporated magnetic tape by the thin film magnetic head with the operation magnetic gap having the asymmetric structure, a problem arises, in which an S/N (signal-to-noise ratio) is considerably lowered by off-track in which the thin film magnetic head is shifted from the center of the track upon reproduction.